Numerous protective coatings for lenses are known to the art. Most of these coatings are thermally cured polymeric films whose composition establishes a matrix, which may possibly include functional moieties or have an appropriate degree of cross-linking resulting in a corresponding degree of porosity. The thermally cured coatings are principally the result of condensation polymerizations in which water or alcohols are driven off at high temperatures as the polymerization reaction goes to completion, the polysiloxanes being highly representative of this type of polymer.
If such coatings are to be rendered tintable, they must be formulated to include monomers having functional groups which remain unreacted in the polymerization and which are capable of binding subsequently introduced dye molecules. Alternatively, they must be cross-linked to only a limited extent so that the polymeric coating is of such porosity as to constitute a pass-through coating for the dyes. Examples of these types of tintable coatings are described in January U.S. Pat. No. 4,355,135, Suzuki et al. U.S. Pat. No. 4,211,823, and Rotenberg et al. U.S. Pat. Nos. 4,229,228 and 4,173,490.
Polymeric systems which are to serve as protective coatings can also be systems whose polymerization is radiation induced. Such systems generally involve chemically unsaturated functional groups such as vinyl or acrylic moieties. When such systems are exposed to ultraviolet (UV) radiation, radical chain polymerization, otherwise known as addition polymerization, occurs. The nature of radiation curing and the ease with which it can be used make it a highly desirable method for polymerizing protective coatings. Cure times are very short relative to thermal cure times, and the initiation and termination of the polymerization are both virtually instantaneous since they are determined by the time involved engaging or disengaging the radiation source. Examples of radiation-curable coatings are described in Tu et al. U.S. Pat. No. 4,319,811, Chung U.S. Pat. No. 4,348,462, and Matsuo et al. U.S. Pat. No. 3,968,309.
Radiation-polymerizable coatings are generally untintable once they have been applied to a substrate and cured by exposure to radiation. Instead, the desired tint must be added to the original coating formulation before its application to the substrate, as suggested in each of the three patents identified in the preceding paragraph. However, adding the dye to the coating composition before it is applied to the lens requires that separate coating procedures be employed for each desired color and degree of tint and, further, that the lens finisher retain a stock of lenses for each such tint combination desired.
Kamada et al. U.S. Pat. No. 4,291,097 discloses a radiation-curable abrasion-resistant coating composition which is said to be tintable after it has been cured. However, the relatively long dyeing time of one hour specified in the examples given suggests that the tinting process, while feasible, is relatively slow for the coating composition disclosed.